A test can be done to measure the amount of urea nitrogen in the blood.

Alternative Names:

Blood urea nitrogen

How the test is performed:

Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

How to prepare for the test:

Many drugs affect BUN levels. Before having this test, make sure the health care provider knows which medications you are taking.

Drugs that can increase BUN measurements include:

Allopurinol

Aminoglycosides

Amphotericin B

Aspirin (high doses)

Bacitracin

Carbamazepine

Cephalosporins

Chloral hydrate

Cisplatin

Colistin

Furosemide

Gentamicin

Guanethidine

Indomethacin

Methicillin

Methotrexate

Methyldopa

Neomycin

Penicillamine

Polymyxin B

Probenecid

Propranolol

Rifampin

Spironolactone

Tetracyclines

Thiazide diuretics

Triamterene

Vancomycin

Drugs that can decrease BUN measurements include:

Chloramphenicol

Streptomycin

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

The BUN test is often done to check kidney function.

Normal Values:

7 - 20 mg/dL. Note that normal values may vary among different laboratories.